I’m pretty sure she doesn’t need to breathe, however she doesn’t seem suited for aquatic locomotion. She hovers over the ground, yes, but can she swim? Those tentacles, scythes and thin arms do not appear suited to the task. She’d be stuck at the bottom of the ocean.

There are several problems with Wraith sustaining an aquatic lifestyle, which I’ll try to elaborate without insanely complicated science nonsense (per request).

The Obvious: Look what happens to her when you run her through a pond on the planet Shear. She rears upright to keep her head above water and slows to an absolute crawl. Doesn’t seem like she’s overly fond of the “through the river” mode of transport.

An aquatic critter would need longer tentacles to move efficiently in water (look up a picture of an eel - long, but very streamlined).

@MidnightRoses adequately pointed out that she doesn’t seem to need to breathe, but if she were intended for aquatic life of any sort I would expect to see some sort of gills, or other way to oxygenate while underwater.

Look what happens to her when you run her through a pond on the planet Shear. She rears upright to keep her head above water and slows to an absolute crawl. Doesn’t seem like she’s overly fond of the “through the river” mode of transport.

They need to do this so monsters are visible while in the water. I don’t know if it has any basis in what landscapes monsters are capable of traversing in.

@midnightroses the idea behind the scythe is that to grip, you’d get more stability diging them in to the muck of the sea bed. Rather than using her claws. Think like digging an ice pick into the ice, this creates stability and on a horizontal plane, possibly speed.